Carbon pitch workers

The introduction of HPCF by Union Carbide in the USA initiated intensive research and development to improve the processability of mesophase pitch (MP). Riggs and Diefendorf in the US worked on a neo-mesophase pitch based on a solvent extraction technique. Yamada and co-workers discovered the pre-mesophase pitch [41,42] using hydrogenation followed by a rapid heat treatment, while workers at the Kyushu Industrial Research Institute in Japan hydrogenated an anisotropic pitch (preferably a coal tar pitch), which after heat treatment produced a dormant mesophase pitch [43,44], a process known as the Kyukoshi method and able to produce a type of carbon fiber intermediate between a GP and HP fiber. Mochida and co-workers used a Lewis acid, such as AICI3, for the catalytic polymerization of an isotropic pitch, but found that an excessive amount of catalyst was required to achieve mesophase formation. 

Matsumoto and Mochida [33], using NMR with a hydrogenated coal tar pitch mesophase carbon fiber, showed that the initial attack by oxygen was on -CH3 and -CH2- groups, with the gradual formation of carboxyls, esters and aryl carbonyls. Fairly stable cross-links were formed via phenols, ethers and esters. The workers also found that slower heating rates (0.5°C/min instead of 2.0°C/min) produced better mechanical properties and that the final choice would be controlled by the desired target properties and economics. 

In 1984, DuPont acquired the Exxon pitch based carbon fiber business and it was highly probable that the DuPont fibers were based on the Exxon patents [58] using a neophase pitch, which had been extracted with solvent, as precursor material. Initial studies revealed an oriented core microstructure [59]. Later work showed E130 to have an oriented core [60], or radial [61], but all workers agreed that there were many disclinations, which is consistent with the low graphitizability of the fiber. Kogure, Sines and Lavin [61] are insistent that... 

Other workers [117-119] have examined PAN based carbon fibers with STM. Effler et al [120] used STM in conjunction with X-ray analyzes to examine mesophase pitch based carbon fibers. Hoffman and co-workers [121] describe the advantages of STM for studying surface treated carbon fibers. 

Brown et al [118] used AFM to study PAN based carbon fiber in air, Hoffman [119] studied surface treated carbon fiber and Effler et al [120] examined mesophase pitch based carbon fiber. A number of workers [121-123] have used AFM to study carbon fibers. Zhdan and co-workers [124—126] have described the use of AFM at Surrey University to study carbon fibers and Figures 12.52 and 12.53 show AFM images of carbon fiber. 

The term Brooks and Taylor structure is recommended to describe the particular lamellar morphology of the spherules most commonly precipitated from pyrolyzed PITCH. The term honors the workers who first recognized the significance of caxbonaceous mesophase to carbon science and technology and who first defined this spherical morphology. The term Brooks and Taylor structure does not cover all structures found in the spherical mesophase, because other lamellar arrangements have been observed. 

Occupational inhalation exposures occur during the handling of coke, charcoal, and activated earbon, but there is little information on concentrations and sizes of the suspended particles. There are no exposure standards for these materials, aside from nonspecific dust standards, although there are standards for coal tar pitch (10). Similar to other dusts, these materials may cause transient reductions of lung function or aggravation of other respiratory symptoms on brief, high-level exposure. Pneumoconiosis from coke or charcoal dust is possible with heavy exposures, but little information has been reported. Pneumoconiosis has been reported in workers manufacturing carbon electrodes from coke (77) and from occupational exposures to activated carbon (78). 

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